Switches and information products sometimes need to get more power than the product to which they are connected can supply. In this case, we usually use an external power supply to expand the power to the external products. For example, Power Over Ethernet (PoE) switches and External Power Supply (EPS) products. PoE Switch with the EPS product can increase the power supply capacity of PoE switch, such as: PoE Switch have 48 ports and can support 12 PoE ports, and each Port can supply 30 W, but it would support 24 PoE ports or 48 PoE ports if connected with the EPS products. However, when EPS cable cannot supply power to the switch system due to failure, the switch system will not be able to provide the power provided by the original system and EPS products, causing system overload, so that the system stops operation.